In recent years, the Internet has rapidly spread throughout the world, and communication systems using the Internet have been gaining attention. Various communication systems have been proposed, such as instant message systems which exchange messages by transmitting/receiving text, internet telephones which exchanges audio data by VoIP (Voice Over IP), and furthermore, television conference systems and Internet television telephones which exchange video data as well as the audio data. The communication systems which use these VoIP technologies such as the television telephone, use protocols such as ITU-T recommended H. 323, IETF standard technology SIP (Session Initiation Protocol), RTP (Real-Time Transport Protocol), or the like.
These communication systems which use the Internet technologies are different to the conventional communication means such as a telephone; it is easy to implement complex functions combining other internet technologies into one. The following is one example which may be considered: A content data set is shared between communication devices which function as communication system terminals. Users participating in a call or a conference may view and listen to the shared content items at the same time.
When the content data is shared in the communication system, a user which proposes to share data (hereafter referred as a master user) specifies a content item the user intends to share, and notifies a user which receives the data (hereafter referred as a slave user) of the content data or information in order to obtain the content data. This starts the sharing of the content item.
The shared content items include content items available for anyone to obtain from the Internet, such as web contents. The shared content items may also be personally owned contents obtained from a digital camera, a digital video camera, a portable phone, or other devices.
If the content items on the Internet are shared, the content items may be shared as follows: a URL of the content data is shared between the communication device of the master user and the communication device of the slave user, and both devices download the data in accordance with the URL.
A sharing method described in Patent Document 1 is known as a method to realize the share of content, for example. In the method described in Patent Document 1, a master portable phone obtains content data from a web server, and transmits a URL of the content data to a slave portable phone at the same time, via a control device in the network. The slave portable phone then obtains the content data in accordance with the received URL. This enables both the master and slave portable phones to obtain and display the content data.
A sharing system described in Patent Document 2 is known as a sharing system to share personally owned content items, for example. In the content sharing system described in Patent Document 2, a master terminal reproduces the content data recorded on a storage medium such as a DVD. The content data is reproduced by reproduction means of a disk drive and the like provided in the master terminal. At the same time, the master terminal distributes the content data to the slave terminal. This realizes the share of the content items between the master terminal and the slave terminal.
[Patent Document 1]
Japanese Unexamined Patent Publication, Tokukai, No. 2005-210236 (published Aug. 4, 2005)
[Patent Document 2]
Japanese Unexamined Patent Publication, Tokukai, No. 2005-229522 (published Aug. 25, 2005)